This invention relates to a process for the production of a cyclic ether directly from an ester of acetic acid and a 1,4-glycol. More particularly, the present invention is directed to an improved process for the production of tetrahydrofuran or dihydrofuran from an ester of acetic acid and 1,4-butanediol or 1,4-dihydroxybutene-2.
Tetrahydrofuran is useful as a solvent for various substances, especially as a solvent for high molecular weight substances such as polyvinyl chloride, polyvinylidene chloride and the like. A variety of processes have been hitherto known for the production of tetrahydrofuran, e.g. a process wherein furan obtained by decarbonylation of furfral is subjected to a catalytic hydrogenation, a process including hydrogenating a butynediol obtained by the reaction of acetylene with formaldehyde to form a butanediol product followed by dehydrative cyclization of the product, and a process including reacting 1,4-butanediol diacetate with water in the presence of an acid catalyst (Refer to British Patent No. 1,170,222).
In the production of a cyclic ether, especially tetrahydrofuran, from an ester of acetic acid and a 1,4-glycol, it is known to be advantageous to bring water in excess of the stoichiometric amount and in the form of steam, into a gas-liquid counter-current flow contact with the ester, because the cyclic ether is produced with high conversion rate and is recovered from the gas-liquid contacting zone as a gas phase (Refer to Offenlegungsshrift Nos. 2,415,663 and 2,456,780).
In this process, the reaction is performed in the presence of an acid catalyst. When a non-volatile, liquid acid catalyst is used, however, it is very difficult to prevent high boiling point by-products from being produced. The production of such high boiling point substances is very disadvantageous not only because it causes lowering of the yield of the cyclic ether but also because it necessitates complicated procedures at a distillation step for the recovery of the product and the catalyst. Moreover, these by-products have a tendency to deposite to the wall of a reaction vessel, resulting in the lowering of heat transmission efficiency of the reactor.
The present inventor has made many researches for developing processes for the production of a cyclic ether from an ester of acetic acid and a 1,4-glycol by the reaction with water in the presence of an acid catalyst. As a result of the researches, it has been found that high boiling point substances secondarily produced in the course of the cyclization reaction, can be easily solidified by a simple way and can be separated by filtration. The present invention is based on this finding.